Before they could slip away for the summer recess, Silvio Berlusconi called about 30 of his MPs to a meeting in his 17th-century Roman palazzo, where an "escort", Patrizia D'Addario, claims to have recorded her pillow talk with him.

According to an account in the newspaper La Repubblica, as the meeting was about to break up, Italy's prime minister, who recently admitted he was "no saint", asked his followers: "Have you heard the latest one about La D'Addario?" Egged on by their denials, he is reported to have added: "She says Berlusconi may not, in fact, be a saint. But he fucks like a god!"

As millions of Italians yesterday packed for their holidays and prepared to forget politics till the autumn, their endlessly controversial leader never looked less like resigning. Newspapers worldwide may have written off his chances of surviving a double-barrelled scandal that would long ago have felled even the most revered statesman elsewhere. But Berlusconi seems bullet-proof.

He could, of course, fall to new revelations. In an apparent reference to her night with the Prime Minister, Patrizia D'Addario said on Friday night : "At those parties in which I took part worse things happened, I can assure you."

But if a 72-year-old married grandfather can get away with refusing to explain his relationship with a girl of 18 and then survive the dissemination of a recording in which he purportedly discusses orgasms and masturbation while in bed with a prostitute, it may be wondered what could possibly bring him down. The last seven days, moreover, have seen Berlusconi's position shored up on two fronts.

On Thursday, Italians were given a dramatic reminder that the investigation that brought to light their prime minister's relationship with D'Addario and other "escorts" was not directed at possible wrongdoing on the right but the left. Police in Bari raided the offices of five opposition parties. They were armed with warrants issued by prosecutors looking into suspected illegal party funding over a period from 2005 to the present. Bari is the capital of Apulia, a region governed by Nichi Vendola, one of the left's few charismatic figures.

The suspicion is that politicians in his administration steered health service contracts to suppliers in exchange for kickbacks to their parties' coffers. Among the prosecutors is one attached to the organised crime department - indicating the possible involvement of Apulia's mafia.

Vendola has denied wrongdoing and no charges have been laid.

But, for some, the raids put a different slant on the Berlusconi scandals. "It is to be asked whether the fierce attacks by the entire opposition front on the prime minister and his undoubtedly questionable behaviour might not perhaps have sought to cover up fears of what the inquiry could bring to light," wrote a Corriere della Sera commentator, Antonio Macaluso.

Apulia was not the only part of the south on Berlusconi's mind last week, as he sought to put down a rebellion in his party. His Freedom People movement is allied to two regional groups: the Northern League and a smaller group, the MPA, which seeks broader self-government for Sicily.

Exasperated by what he saw as the prime minister's repeated concessions to the League, a junior minister, Gianfranco Miccichè, threatened to lead a group of fellow rebels out of the Freedom People and link up with the MPA. The aim was to create a new "Party of the South" that would enjoy the same leverage as the League, on which the government relies for its majority.

By yesterday Berlusconi had neutralised the threat in the time-honoured fashion of Italian prime ministers - by throwing money at the Mezzogiorno. He promised to unblock some €4bn of development funds for Sicily, start talks on extra financing for other southern regions, and create a new government agency and public bank for the Mezzogiorno.

But the speed with which the revolt was stifled diverted attention from two facts that could foreshadow trouble for Italy's ebullient leader when politics return to normal in the autumn. This was the first internal party revolt Berlusconi has faced. The scandals may not have finished him, but they have weakened him.

It was perhaps no coincidence that when the most senior member of his cabinet, finance minister Giulio Tremonti, was interviewed on television on Friday, he was asked if he considered himself Berlusconi's heir. Tremonti replied that it was difficult "to imagine succeeding such an extraordinary person". Which was not quite a denial.